My prediction is that the sign up banner is not showing for certain phones and it's a separate issue. The beta will fill out and we'll be left out despite support telling me it's just a rollout issue and another rep telling me it's not out for anyone yet. This exact same problem happened on my Note 8. Samsung really handcuffs their support staff as it seems they have zero info or resources to actually do any service side troubleshooting or escalations.
I got the banner to sign up for the Beta program last night. I immediately register but I didn't get a feedback that my registration had gone through. So, I did it again, more than once. This morning I requested the latest upgrade and I got the November security patch. I am still hoping Samsung took my registration. I want to see if Samsung is implementing RCS in one UI 2 Messages application since it is very aggressive over Google Messaging.
I got the banner today and I immediately went to the settings/system update, and there it was... Sadly now my recent apps button isn't working any more, I reset settings and cleared cache and still no luck... I guess I wait for another update. I hope I don't have to do a full reset.